Once you have done the reflash, if you have any problems afterwards there's a section in the wiki that that advises fiashing the rootfs first and then the EMMC followed by the rootfs again. Don't usr the -R switch at the end of the command on the first 2 flashes. It may also be a good idea to NOT restore a full backup in case you restore some corrupted settings. Just restore communication and contact settings

And just for the record. It's virtually impossible to kill your N900 unless you physically smash it or sink it in a bucket of water. I've seen them brought back to life from some of the worst situations.